… | |
… | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
|
|
14 | #include <stdio.h> // for puts |
|
|
15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
… | |
… | |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
276 | |
278 | |
277 | =back |
279 | =back |
278 | |
280 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
281 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
282 | |
281 | An event loop is described by a C<ev_loop *>. The library knows two |
283 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
282 | types of such loops, the I<default> loop, which supports signals and child |
284 | is I<not> optional in this case, as there is also an C<ev_loop> |
283 | events, and dynamically created loops which do not. |
285 | I<function>). |
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286 | |
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287 | The library knows two types of such loops, the I<default> loop, which |
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288 | supports signals and child events, and dynamically created loops which do |
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289 | not. |
284 | |
290 | |
285 | =over 4 |
291 | =over 4 |
286 | |
292 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
293 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
294 | |
… | |
… | |
294 | If you don't know what event loop to use, use the one returned from this |
300 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
301 | function. |
296 | |
302 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
303 | Note that this function is I<not> thread-safe, so if you want to use it |
298 | from multiple threads, you have to lock (note also that this is unlikely, |
304 | from multiple threads, you have to lock (note also that this is unlikely, |
299 | as loops cannot bes hared easily between threads anyway). |
305 | as loops cannot be shared easily between threads anyway). |
300 | |
306 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
307 | The default loop is the only loop that can handle C<ev_signal> and |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
308 | C<ev_child> watchers, and to do this, it always registers a handler |
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
309 | for C<SIGCHLD>. If this is a problem for your application you can either |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
310 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
386 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
381 | |
387 | |
382 | For few fds, this backend is a bit little slower than poll and select, |
388 | For few fds, this backend is a bit little slower than poll and select, |
383 | but it scales phenomenally better. While poll and select usually scale |
389 | but it scales phenomenally better. While poll and select usually scale |
384 | like O(total_fds) where n is the total number of fds (or the highest fd), |
390 | like O(total_fds) where n is the total number of fds (or the highest fd), |
385 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
391 | epoll scales either O(1) or O(active_fds). |
386 | of shortcomings, such as silently dropping events in some hard-to-detect |
392 | |
387 | cases and requiring a system call per fd change, no fork support and bad |
393 | The epoll mechanism deserves honorable mention as the most misdesigned |
388 | support for dup. |
394 | of the more advanced event mechanisms: mere annoyances include silently |
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395 | dropping file descriptors, requiring a system call per change per file |
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396 | descriptor (and unnecessary guessing of parameters), problems with dup and |
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397 | so on. The biggest issue is fork races, however - if a program forks then |
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398 | I<both> parent and child process have to recreate the epoll set, which can |
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399 | take considerable time (one syscall per file descriptor) and is of course |
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400 | hard to detect. |
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401 | |
|
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402 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
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403 | of course I<doesn't>, and epoll just loves to report events for totally |
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404 | I<different> file descriptors (even already closed ones, so one cannot |
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405 | even remove them from the set) than registered in the set (especially |
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406 | on SMP systems). Libev tries to counter these spurious notifications by |
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407 | employing an additional generation counter and comparing that against the |
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408 | events to filter out spurious ones, recreating the set when required. |
389 | |
409 | |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
410 | While stopping, setting and starting an I/O watcher in the same iteration |
391 | will result in some caching, there is still a system call per such incident |
411 | will result in some caching, there is still a system call per such |
392 | (because the fd could point to a different file description now), so its |
412 | incident (because the same I<file descriptor> could point to a different |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
413 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
394 | very well if you register events for both fds. |
414 | file descriptors might not work very well if you register events for both |
395 | |
415 | file descriptors. |
396 | Please note that epoll sometimes generates spurious notifications, so you |
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397 | need to use non-blocking I/O or other means to avoid blocking when no data |
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398 | (or space) is available. |
|
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399 | |
416 | |
400 | Best performance from this backend is achieved by not unregistering all |
417 | Best performance from this backend is achieved by not unregistering all |
401 | watchers for a file descriptor until it has been closed, if possible, |
418 | watchers for a file descriptor until it has been closed, if possible, |
402 | i.e. keep at least one watcher active per fd at all times. Stopping and |
419 | i.e. keep at least one watcher active per fd at all times. Stopping and |
403 | starting a watcher (without re-setting it) also usually doesn't cause |
420 | starting a watcher (without re-setting it) also usually doesn't cause |
404 | extra overhead. |
421 | extra overhead. A fork can both result in spurious notifications as well |
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|
422 | as in libev having to destroy and recreate the epoll object, which can |
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423 | take considerable time and thus should be avoided. |
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424 | |
|
|
425 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
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|
426 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
427 | the usage. So sad. |
405 | |
428 | |
406 | While nominally embeddable in other event loops, this feature is broken in |
429 | While nominally embeddable in other event loops, this feature is broken in |
407 | all kernel versions tested so far. |
430 | all kernel versions tested so far. |
408 | |
431 | |
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
432 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
410 | C<EVBACKEND_POLL>. |
433 | C<EVBACKEND_POLL>. |
411 | |
434 | |
412 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
435 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
413 | |
436 | |
414 | Kqueue deserves special mention, as at the time of this writing, it was |
437 | Kqueue deserves special mention, as at the time of this writing, it |
415 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
438 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
416 | anything but sockets and pipes, except on Darwin, where of course it's |
439 | with anything but sockets and pipes, except on Darwin, where of course |
417 | completely useless). For this reason it's not being "auto-detected" unless |
440 | it's completely useless). Unlike epoll, however, whose brokenness |
418 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
441 | is by design, these kqueue bugs can (and eventually will) be fixed |
419 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
442 | without API changes to existing programs. For this reason it's not being |
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|
443 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
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444 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
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445 | system like NetBSD. |
420 | |
446 | |
421 | You still can embed kqueue into a normal poll or select backend and use it |
447 | You still can embed kqueue into a normal poll or select backend and use it |
422 | only for sockets (after having made sure that sockets work with kqueue on |
448 | only for sockets (after having made sure that sockets work with kqueue on |
423 | the target platform). See C<ev_embed> watchers for more info. |
449 | the target platform). See C<ev_embed> watchers for more info. |
424 | |
450 | |
425 | It scales in the same way as the epoll backend, but the interface to the |
451 | It scales in the same way as the epoll backend, but the interface to the |
426 | kernel is more efficient (which says nothing about its actual speed, of |
452 | kernel is more efficient (which says nothing about its actual speed, of |
427 | course). While stopping, setting and starting an I/O watcher does never |
453 | course). While stopping, setting and starting an I/O watcher does never |
428 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
454 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
429 | two event changes per incident. Support for C<fork ()> is very bad and it |
455 | two event changes per incident. Support for C<fork ()> is very bad (but |
430 | drops fds silently in similarly hard-to-detect cases. |
456 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
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|
457 | cases |
431 | |
458 | |
432 | This backend usually performs well under most conditions. |
459 | This backend usually performs well under most conditions. |
433 | |
460 | |
434 | While nominally embeddable in other event loops, this doesn't work |
461 | While nominally embeddable in other event loops, this doesn't work |
435 | everywhere, so you might need to test for this. And since it is broken |
462 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
464 | might perform better. |
491 | might perform better. |
465 | |
492 | |
466 | On the positive side, with the exception of the spurious readiness |
493 | On the positive side, with the exception of the spurious readiness |
467 | notifications, this backend actually performed fully to specification |
494 | notifications, this backend actually performed fully to specification |
468 | in all tests and is fully embeddable, which is a rare feat among the |
495 | in all tests and is fully embeddable, which is a rare feat among the |
469 | OS-specific backends. |
496 | OS-specific backends (I vastly prefer correctness over speed hacks). |
470 | |
497 | |
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
498 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
472 | C<EVBACKEND_POLL>. |
499 | C<EVBACKEND_POLL>. |
473 | |
500 | |
474 | =item C<EVBACKEND_ALL> |
501 | =item C<EVBACKEND_ALL> |
… | |
… | |
527 | responsibility to either stop all watchers cleanly yourself I<before> |
554 | responsibility to either stop all watchers cleanly yourself I<before> |
528 | calling this function, or cope with the fact afterwards (which is usually |
555 | calling this function, or cope with the fact afterwards (which is usually |
529 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
556 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
530 | for example). |
557 | for example). |
531 | |
558 | |
532 | Note that certain global state, such as signal state, will not be freed by |
559 | Note that certain global state, such as signal state (and installed signal |
533 | this function, and related watchers (such as signal and child watchers) |
560 | handlers), will not be freed by this function, and related watchers (such |
534 | would need to be stopped manually. |
561 | as signal and child watchers) would need to be stopped manually. |
535 | |
562 | |
536 | In general it is not advisable to call this function except in the |
563 | In general it is not advisable to call this function except in the |
537 | rare occasion where you really need to free e.g. the signal handling |
564 | rare occasion where you really need to free e.g. the signal handling |
538 | pipe fds. If you need dynamically allocated loops it is better to use |
565 | pipe fds. If you need dynamically allocated loops it is better to use |
539 | C<ev_loop_new> and C<ev_loop_destroy>). |
566 | C<ev_loop_new> and C<ev_loop_destroy>). |
… | |
… | |
631 | the loop. |
658 | the loop. |
632 | |
659 | |
633 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
660 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
634 | necessary) and will handle those and any already outstanding ones. It |
661 | necessary) and will handle those and any already outstanding ones. It |
635 | will block your process until at least one new event arrives (which could |
662 | will block your process until at least one new event arrives (which could |
636 | be an event internal to libev itself, so there is no guarentee that a |
663 | be an event internal to libev itself, so there is no guarantee that a |
637 | user-registered callback will be called), and will return after one |
664 | user-registered callback will be called), and will return after one |
638 | iteration of the loop. |
665 | iteration of the loop. |
639 | |
666 | |
640 | This is useful if you are waiting for some external event in conjunction |
667 | This is useful if you are waiting for some external event in conjunction |
641 | with something not expressible using other libev watchers (i.e. "roll your |
668 | with something not expressible using other libev watchers (i.e. "roll your |
… | |
… | |
768 | they fire on, say, one-second boundaries only. |
795 | they fire on, say, one-second boundaries only. |
769 | |
796 | |
770 | =item ev_loop_verify (loop) |
797 | =item ev_loop_verify (loop) |
771 | |
798 | |
772 | This function only does something when C<EV_VERIFY> support has been |
799 | This function only does something when C<EV_VERIFY> support has been |
773 | compiled in. which is the default for non-minimal builds. It tries to go |
800 | compiled in, which is the default for non-minimal builds. It tries to go |
774 | through all internal structures and checks them for validity. If anything |
801 | through all internal structures and checks them for validity. If anything |
775 | is found to be inconsistent, it will print an error message to standard |
802 | is found to be inconsistent, it will print an error message to standard |
776 | error and call C<abort ()>. |
803 | error and call C<abort ()>. |
777 | |
804 | |
778 | This can be used to catch bugs inside libev itself: under normal |
805 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
781 | |
808 | |
782 | =back |
809 | =back |
783 | |
810 | |
784 | |
811 | |
785 | =head1 ANATOMY OF A WATCHER |
812 | =head1 ANATOMY OF A WATCHER |
|
|
813 | |
|
|
814 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
815 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
816 | watchers and C<ev_io_start> for I/O watchers. |
786 | |
817 | |
787 | A watcher is a structure that you create and register to record your |
818 | A watcher is a structure that you create and register to record your |
788 | interest in some event. For instance, if you want to wait for STDIN to |
819 | interest in some event. For instance, if you want to wait for STDIN to |
789 | become readable, you would create an C<ev_io> watcher for that: |
820 | become readable, you would create an C<ev_io> watcher for that: |
790 | |
821 | |
… | |
… | |
793 | ev_io_stop (w); |
824 | ev_io_stop (w); |
794 | ev_unloop (loop, EVUNLOOP_ALL); |
825 | ev_unloop (loop, EVUNLOOP_ALL); |
795 | } |
826 | } |
796 | |
827 | |
797 | struct ev_loop *loop = ev_default_loop (0); |
828 | struct ev_loop *loop = ev_default_loop (0); |
|
|
829 | |
798 | ev_io stdin_watcher; |
830 | ev_io stdin_watcher; |
|
|
831 | |
799 | ev_init (&stdin_watcher, my_cb); |
832 | ev_init (&stdin_watcher, my_cb); |
800 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
833 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
801 | ev_io_start (loop, &stdin_watcher); |
834 | ev_io_start (loop, &stdin_watcher); |
|
|
835 | |
802 | ev_loop (loop, 0); |
836 | ev_loop (loop, 0); |
803 | |
837 | |
804 | As you can see, you are responsible for allocating the memory for your |
838 | As you can see, you are responsible for allocating the memory for your |
805 | watcher structures (and it is usually a bad idea to do this on the stack, |
839 | watcher structures (and it is I<usually> a bad idea to do this on the |
806 | although this can sometimes be quite valid). |
840 | stack). |
|
|
841 | |
|
|
842 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
843 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
807 | |
844 | |
808 | Each watcher structure must be initialised by a call to C<ev_init |
845 | Each watcher structure must be initialised by a call to C<ev_init |
809 | (watcher *, callback)>, which expects a callback to be provided. This |
846 | (watcher *, callback)>, which expects a callback to be provided. This |
810 | callback gets invoked each time the event occurs (or, in the case of I/O |
847 | callback gets invoked each time the event occurs (or, in the case of I/O |
811 | watchers, each time the event loop detects that the file descriptor given |
848 | watchers, each time the event loop detects that the file descriptor given |
812 | is readable and/or writable). |
849 | is readable and/or writable). |
813 | |
850 | |
814 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
851 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
815 | with arguments specific to this watcher type. There is also a macro |
852 | macro to configure it, with arguments specific to the watcher type. There |
816 | to combine initialisation and setting in one call: C<< ev_<type>_init |
853 | is also a macro to combine initialisation and setting in one call: C<< |
817 | (watcher *, callback, ...) >>. |
854 | ev_TYPE_init (watcher *, callback, ...) >>. |
818 | |
855 | |
819 | To make the watcher actually watch out for events, you have to start it |
856 | To make the watcher actually watch out for events, you have to start it |
820 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
857 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
821 | *) >>), and you can stop watching for events at any time by calling the |
858 | *) >>), and you can stop watching for events at any time by calling the |
822 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
859 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
823 | |
860 | |
824 | As long as your watcher is active (has been started but not stopped) you |
861 | As long as your watcher is active (has been started but not stopped) you |
825 | must not touch the values stored in it. Most specifically you must never |
862 | must not touch the values stored in it. Most specifically you must never |
826 | reinitialise it or call its C<set> macro. |
863 | reinitialise it or call its C<ev_TYPE_set> macro. |
827 | |
864 | |
828 | Each and every callback receives the event loop pointer as first, the |
865 | Each and every callback receives the event loop pointer as first, the |
829 | registered watcher structure as second, and a bitset of received events as |
866 | registered watcher structure as second, and a bitset of received events as |
830 | third argument. |
867 | third argument. |
831 | |
868 | |
… | |
… | |
912 | |
949 | |
913 | =back |
950 | =back |
914 | |
951 | |
915 | =head2 GENERIC WATCHER FUNCTIONS |
952 | =head2 GENERIC WATCHER FUNCTIONS |
916 | |
953 | |
917 | In the following description, C<TYPE> stands for the watcher type, |
|
|
918 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
919 | |
|
|
920 | =over 4 |
954 | =over 4 |
921 | |
955 | |
922 | =item C<ev_init> (ev_TYPE *watcher, callback) |
956 | =item C<ev_init> (ev_TYPE *watcher, callback) |
923 | |
957 | |
924 | This macro initialises the generic portion of a watcher. The contents |
958 | This macro initialises the generic portion of a watcher. The contents |
… | |
… | |
1032 | The default priority used by watchers when no priority has been set is |
1066 | The default priority used by watchers when no priority has been set is |
1033 | always C<0>, which is supposed to not be too high and not be too low :). |
1067 | always C<0>, which is supposed to not be too high and not be too low :). |
1034 | |
1068 | |
1035 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1069 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1036 | fine, as long as you do not mind that the priority value you query might |
1070 | fine, as long as you do not mind that the priority value you query might |
1037 | or might not have been adjusted to be within valid range. |
1071 | or might not have been clamped to the valid range. |
1038 | |
1072 | |
1039 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1073 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1040 | |
1074 | |
1041 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1075 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1042 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1076 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1387 | else |
1421 | else |
1388 | { |
1422 | { |
1389 | // callback was invoked, but there was some activity, re-arm |
1423 | // callback was invoked, but there was some activity, re-arm |
1390 | // the watcher to fire in last_activity + 60, which is |
1424 | // the watcher to fire in last_activity + 60, which is |
1391 | // guaranteed to be in the future, so "again" is positive: |
1425 | // guaranteed to be in the future, so "again" is positive: |
1392 | w->again = timeout - now; |
1426 | w->repeat = timeout - now; |
1393 | ev_timer_again (EV_A_ w); |
1427 | ev_timer_again (EV_A_ w); |
1394 | } |
1428 | } |
1395 | } |
1429 | } |
1396 | |
1430 | |
1397 | To summarise the callback: first calculate the real timeout (defined |
1431 | To summarise the callback: first calculate the real timeout (defined |
… | |
… | |
1426 | |
1460 | |
1427 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1461 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1428 | callback :) - just change the timeout and invoke the callback, which will |
1462 | callback :) - just change the timeout and invoke the callback, which will |
1429 | fix things for you. |
1463 | fix things for you. |
1430 | |
1464 | |
1431 | =item 4. Whee, use a double-linked list for your timeouts. |
1465 | =item 4. Wee, just use a double-linked list for your timeouts. |
1432 | |
1466 | |
1433 | If there is not one request, but many thousands, all employing some kind |
1467 | If there is not one request, but many thousands (millions...), all |
1434 | of timeout with the same timeout value, then one can do even better: |
1468 | employing some kind of timeout with the same timeout value, then one can |
|
|
1469 | do even better: |
1435 | |
1470 | |
1436 | When starting the timeout, calculate the timeout value and put the timeout |
1471 | When starting the timeout, calculate the timeout value and put the timeout |
1437 | at the I<end> of the list. |
1472 | at the I<end> of the list. |
1438 | |
1473 | |
1439 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
1474 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
… | |
… | |
1448 | complication, and having to use a constant timeout. The constant timeout |
1483 | complication, and having to use a constant timeout. The constant timeout |
1449 | ensures that the list stays sorted. |
1484 | ensures that the list stays sorted. |
1450 | |
1485 | |
1451 | =back |
1486 | =back |
1452 | |
1487 | |
1453 | So what method is the best? |
1488 | So which method the best? |
1454 | |
1489 | |
1455 | The method #2 is a simple no-brain-required solution that is adequate in |
1490 | Method #2 is a simple no-brain-required solution that is adequate in most |
1456 | most situations. Method #3 requires a bit more thinking, but handles many |
1491 | situations. Method #3 requires a bit more thinking, but handles many cases |
1457 | cases better, and isn't very complicated either. In most case, choosing |
1492 | better, and isn't very complicated either. In most case, choosing either |
1458 | either one is fine. |
1493 | one is fine, with #3 being better in typical situations. |
1459 | |
1494 | |
1460 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1495 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1461 | rather complicated, but extremely efficient, something that really pays |
1496 | rather complicated, but extremely efficient, something that really pays |
1462 | off after the first or so million of active timers, i.e. it's usually |
1497 | off after the first million or so of active timers, i.e. it's usually |
1463 | overkill :) |
1498 | overkill :) |
1464 | |
1499 | |
1465 | =head3 The special problem of time updates |
1500 | =head3 The special problem of time updates |
1466 | |
1501 | |
1467 | Establishing the current time is a costly operation (it usually takes at |
1502 | Establishing the current time is a costly operation (it usually takes at |
… | |
… | |
1898 | |
1933 | |
1899 | |
1934 | |
1900 | =head2 C<ev_stat> - did the file attributes just change? |
1935 | =head2 C<ev_stat> - did the file attributes just change? |
1901 | |
1936 | |
1902 | This watches a file system path for attribute changes. That is, it calls |
1937 | This watches a file system path for attribute changes. That is, it calls |
1903 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
1938 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1904 | compared to the last time, invoking the callback if it did. |
1939 | and sees if it changed compared to the last time, invoking the callback if |
|
|
1940 | it did. |
1905 | |
1941 | |
1906 | The path does not need to exist: changing from "path exists" to "path does |
1942 | The path does not need to exist: changing from "path exists" to "path does |
1907 | not exist" is a status change like any other. The condition "path does |
1943 | not exist" is a status change like any other. The condition "path does not |
1908 | not exist" is signified by the C<st_nlink> field being zero (which is |
1944 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1909 | otherwise always forced to be at least one) and all the other fields of |
1945 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1910 | the stat buffer having unspecified contents. |
1946 | least one) and all the other fields of the stat buffer having unspecified |
|
|
1947 | contents. |
1911 | |
1948 | |
1912 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1949 | The path I<must not> end in a slash or contain special components such as |
|
|
1950 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1913 | relative and your working directory changes, the behaviour is undefined. |
1951 | your working directory changes, then the behaviour is undefined. |
1914 | |
1952 | |
1915 | Since there is no standard kernel interface to do this, the portable |
1953 | Since there is no portable change notification interface available, the |
1916 | implementation simply calls C<stat (2)> regularly on the path to see if |
1954 | portable implementation simply calls C<stat(2)> regularly on the path |
1917 | it changed somehow. You can specify a recommended polling interval for |
1955 | to see if it changed somehow. You can specify a recommended polling |
1918 | this case. If you specify a polling interval of C<0> (highly recommended!) |
1956 | interval for this case. If you specify a polling interval of C<0> (highly |
1919 | then a I<suitable, unspecified default> value will be used (which |
1957 | recommended!) then a I<suitable, unspecified default> value will be used |
1920 | you can expect to be around five seconds, although this might change |
1958 | (which you can expect to be around five seconds, although this might |
1921 | dynamically). Libev will also impose a minimum interval which is currently |
1959 | change dynamically). Libev will also impose a minimum interval which is |
1922 | around C<0.1>, but thats usually overkill. |
1960 | currently around C<0.1>, but that's usually overkill. |
1923 | |
1961 | |
1924 | This watcher type is not meant for massive numbers of stat watchers, |
1962 | This watcher type is not meant for massive numbers of stat watchers, |
1925 | as even with OS-supported change notifications, this can be |
1963 | as even with OS-supported change notifications, this can be |
1926 | resource-intensive. |
1964 | resource-intensive. |
1927 | |
1965 | |
1928 | At the time of this writing, the only OS-specific interface implemented |
1966 | At the time of this writing, the only OS-specific interface implemented |
1929 | is the Linux inotify interface (implementing kqueue support is left as |
1967 | is the Linux inotify interface (implementing kqueue support is left as an |
1930 | an exercise for the reader. Note, however, that the author sees no way |
1968 | exercise for the reader. Note, however, that the author sees no way of |
1931 | of implementing C<ev_stat> semantics with kqueue). |
1969 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1932 | |
1970 | |
1933 | =head3 ABI Issues (Largefile Support) |
1971 | =head3 ABI Issues (Largefile Support) |
1934 | |
1972 | |
1935 | Libev by default (unless the user overrides this) uses the default |
1973 | Libev by default (unless the user overrides this) uses the default |
1936 | compilation environment, which means that on systems with large file |
1974 | compilation environment, which means that on systems with large file |
1937 | support disabled by default, you get the 32 bit version of the stat |
1975 | support disabled by default, you get the 32 bit version of the stat |
1938 | structure. When using the library from programs that change the ABI to |
1976 | structure. When using the library from programs that change the ABI to |
1939 | use 64 bit file offsets the programs will fail. In that case you have to |
1977 | use 64 bit file offsets the programs will fail. In that case you have to |
1940 | compile libev with the same flags to get binary compatibility. This is |
1978 | compile libev with the same flags to get binary compatibility. This is |
1941 | obviously the case with any flags that change the ABI, but the problem is |
1979 | obviously the case with any flags that change the ABI, but the problem is |
1942 | most noticeably disabled with ev_stat and large file support. |
1980 | most noticeably displayed with ev_stat and large file support. |
1943 | |
1981 | |
1944 | The solution for this is to lobby your distribution maker to make large |
1982 | The solution for this is to lobby your distribution maker to make large |
1945 | file interfaces available by default (as e.g. FreeBSD does) and not |
1983 | file interfaces available by default (as e.g. FreeBSD does) and not |
1946 | optional. Libev cannot simply switch on large file support because it has |
1984 | optional. Libev cannot simply switch on large file support because it has |
1947 | to exchange stat structures with application programs compiled using the |
1985 | to exchange stat structures with application programs compiled using the |
1948 | default compilation environment. |
1986 | default compilation environment. |
1949 | |
1987 | |
1950 | =head3 Inotify and Kqueue |
1988 | =head3 Inotify and Kqueue |
1951 | |
1989 | |
1952 | When C<inotify (7)> support has been compiled into libev (generally |
1990 | When C<inotify (7)> support has been compiled into libev and present at |
1953 | only available with Linux 2.6.25 or above due to bugs in earlier |
1991 | runtime, it will be used to speed up change detection where possible. The |
1954 | implementations) and present at runtime, it will be used to speed up |
1992 | inotify descriptor will be created lazily when the first C<ev_stat> |
1955 | change detection where possible. The inotify descriptor will be created |
1993 | watcher is being started. |
1956 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1957 | |
1994 | |
1958 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1995 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1959 | except that changes might be detected earlier, and in some cases, to avoid |
1996 | except that changes might be detected earlier, and in some cases, to avoid |
1960 | making regular C<stat> calls. Even in the presence of inotify support |
1997 | making regular C<stat> calls. Even in the presence of inotify support |
1961 | there are many cases where libev has to resort to regular C<stat> polling, |
1998 | there are many cases where libev has to resort to regular C<stat> polling, |
1962 | but as long as the path exists, libev usually gets away without polling. |
1999 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2000 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2001 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2002 | xfs are fully working) libev usually gets away without polling. |
1963 | |
2003 | |
1964 | There is no support for kqueue, as apparently it cannot be used to |
2004 | There is no support for kqueue, as apparently it cannot be used to |
1965 | implement this functionality, due to the requirement of having a file |
2005 | implement this functionality, due to the requirement of having a file |
1966 | descriptor open on the object at all times, and detecting renames, unlinks |
2006 | descriptor open on the object at all times, and detecting renames, unlinks |
1967 | etc. is difficult. |
2007 | etc. is difficult. |
1968 | |
2008 | |
|
|
2009 | =head3 C<stat ()> is a synchronous operation |
|
|
2010 | |
|
|
2011 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2012 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2013 | ()>, which is a synchronous operation. |
|
|
2014 | |
|
|
2015 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2016 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2017 | as the path data is suually in memory already (except when starting the |
|
|
2018 | watcher). |
|
|
2019 | |
|
|
2020 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2021 | time due to network issues, and even under good conditions, a stat call |
|
|
2022 | often takes multiple milliseconds. |
|
|
2023 | |
|
|
2024 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2025 | paths, although this is fully supported by libev. |
|
|
2026 | |
1969 | =head3 The special problem of stat time resolution |
2027 | =head3 The special problem of stat time resolution |
1970 | |
2028 | |
1971 | The C<stat ()> system call only supports full-second resolution portably, and |
2029 | The C<stat ()> system call only supports full-second resolution portably, |
1972 | even on systems where the resolution is higher, most file systems still |
2030 | and even on systems where the resolution is higher, most file systems |
1973 | only support whole seconds. |
2031 | still only support whole seconds. |
1974 | |
2032 | |
1975 | That means that, if the time is the only thing that changes, you can |
2033 | That means that, if the time is the only thing that changes, you can |
1976 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2034 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1977 | calls your callback, which does something. When there is another update |
2035 | calls your callback, which does something. When there is another update |
1978 | within the same second, C<ev_stat> will be unable to detect unless the |
2036 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
2617 | =over 4 |
2675 | =over 4 |
2618 | |
2676 | |
2619 | =item ev_async_init (ev_async *, callback) |
2677 | =item ev_async_init (ev_async *, callback) |
2620 | |
2678 | |
2621 | Initialises and configures the async watcher - it has no parameters of any |
2679 | Initialises and configures the async watcher - it has no parameters of any |
2622 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2680 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2623 | trust me. |
2681 | trust me. |
2624 | |
2682 | |
2625 | =item ev_async_send (loop, ev_async *) |
2683 | =item ev_async_send (loop, ev_async *) |
2626 | |
2684 | |
2627 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2685 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
… | |
… | |
2941 | Tony Arcieri has written a ruby extension that offers access to a subset |
2999 | Tony Arcieri has written a ruby extension that offers access to a subset |
2942 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3000 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2943 | more on top of it. It can be found via gem servers. Its homepage is at |
3001 | more on top of it. It can be found via gem servers. Its homepage is at |
2944 | L<http://rev.rubyforge.org/>. |
3002 | L<http://rev.rubyforge.org/>. |
2945 | |
3003 | |
|
|
3004 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3005 | makes rev work even on mingw. |
|
|
3006 | |
2946 | =item D |
3007 | =item D |
2947 | |
3008 | |
2948 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3009 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2949 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3010 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3011 | |
|
|
3012 | =item Ocaml |
|
|
3013 | |
|
|
3014 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3015 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
2950 | |
3016 | |
2951 | =back |
3017 | =back |
2952 | |
3018 | |
2953 | |
3019 | |
2954 | =head1 MACRO MAGIC |
3020 | =head1 MACRO MAGIC |
… | |
… | |
3055 | |
3121 | |
3056 | #define EV_STANDALONE 1 |
3122 | #define EV_STANDALONE 1 |
3057 | #include "ev.h" |
3123 | #include "ev.h" |
3058 | |
3124 | |
3059 | Both header files and implementation files can be compiled with a C++ |
3125 | Both header files and implementation files can be compiled with a C++ |
3060 | compiler (at least, thats a stated goal, and breakage will be treated |
3126 | compiler (at least, that's a stated goal, and breakage will be treated |
3061 | as a bug). |
3127 | as a bug). |
3062 | |
3128 | |
3063 | You need the following files in your source tree, or in a directory |
3129 | You need the following files in your source tree, or in a directory |
3064 | in your include path (e.g. in libev/ when using -Ilibev): |
3130 | in your include path (e.g. in libev/ when using -Ilibev): |
3065 | |
3131 | |
… | |
… | |
3121 | keeps libev from including F<config.h>, and it also defines dummy |
3187 | keeps libev from including F<config.h>, and it also defines dummy |
3122 | implementations for some libevent functions (such as logging, which is not |
3188 | implementations for some libevent functions (such as logging, which is not |
3123 | supported). It will also not define any of the structs usually found in |
3189 | supported). It will also not define any of the structs usually found in |
3124 | F<event.h> that are not directly supported by the libev core alone. |
3190 | F<event.h> that are not directly supported by the libev core alone. |
3125 | |
3191 | |
|
|
3192 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3193 | configuration, but has to be more conservative. |
|
|
3194 | |
3126 | =item EV_USE_MONOTONIC |
3195 | =item EV_USE_MONOTONIC |
3127 | |
3196 | |
3128 | If defined to be C<1>, libev will try to detect the availability of the |
3197 | If defined to be C<1>, libev will try to detect the availability of the |
3129 | monotonic clock option at both compile time and runtime. Otherwise no use |
3198 | monotonic clock option at both compile time and runtime. Otherwise no |
3130 | of the monotonic clock option will be attempted. If you enable this, you |
3199 | use of the monotonic clock option will be attempted. If you enable this, |
3131 | usually have to link against librt or something similar. Enabling it when |
3200 | you usually have to link against librt or something similar. Enabling it |
3132 | the functionality isn't available is safe, though, although you have |
3201 | when the functionality isn't available is safe, though, although you have |
3133 | to make sure you link against any libraries where the C<clock_gettime> |
3202 | to make sure you link against any libraries where the C<clock_gettime> |
3134 | function is hiding in (often F<-lrt>). |
3203 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3135 | |
3204 | |
3136 | =item EV_USE_REALTIME |
3205 | =item EV_USE_REALTIME |
3137 | |
3206 | |
3138 | If defined to be C<1>, libev will try to detect the availability of the |
3207 | If defined to be C<1>, libev will try to detect the availability of the |
3139 | real-time clock option at compile time (and assume its availability at |
3208 | real-time clock option at compile time (and assume its availability at |
3140 | runtime if successful). Otherwise no use of the real-time clock option will |
3209 | runtime if successful). Otherwise no use of the real-time clock option will |
3141 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3210 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3142 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3211 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3143 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3212 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3144 | |
3213 | |
|
|
3214 | =item EV_USE_CLOCK_SYSCALL |
|
|
3215 | |
|
|
3216 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3217 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3218 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3219 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3220 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3221 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3222 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3223 | higher, as it simplifies linking (no need for C<-lrt>). |
|
|
3224 | |
3145 | =item EV_USE_NANOSLEEP |
3225 | =item EV_USE_NANOSLEEP |
3146 | |
3226 | |
3147 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3227 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3148 | and will use it for delays. Otherwise it will use C<select ()>. |
3228 | and will use it for delays. Otherwise it will use C<select ()>. |
3149 | |
3229 | |
… | |
… | |
3164 | |
3244 | |
3165 | =item EV_SELECT_USE_FD_SET |
3245 | =item EV_SELECT_USE_FD_SET |
3166 | |
3246 | |
3167 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3247 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3168 | structure. This is useful if libev doesn't compile due to a missing |
3248 | structure. This is useful if libev doesn't compile due to a missing |
3169 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3249 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3170 | exotic systems. This usually limits the range of file descriptors to some |
3250 | on exotic systems. This usually limits the range of file descriptors to |
3171 | low limit such as 1024 or might have other limitations (winsocket only |
3251 | some low limit such as 1024 or might have other limitations (winsocket |
3172 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3252 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3173 | influence the size of the C<fd_set> used. |
3253 | configures the maximum size of the C<fd_set>. |
3174 | |
3254 | |
3175 | =item EV_SELECT_IS_WINSOCKET |
3255 | =item EV_SELECT_IS_WINSOCKET |
3176 | |
3256 | |
3177 | When defined to C<1>, the select backend will assume that |
3257 | When defined to C<1>, the select backend will assume that |
3178 | select/socket/connect etc. don't understand file descriptors but |
3258 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3537 | loop, as long as you don't confuse yourself). The only exception is that |
3617 | loop, as long as you don't confuse yourself). The only exception is that |
3538 | you must not do this from C<ev_periodic> reschedule callbacks. |
3618 | you must not do this from C<ev_periodic> reschedule callbacks. |
3539 | |
3619 | |
3540 | Care has been taken to ensure that libev does not keep local state inside |
3620 | Care has been taken to ensure that libev does not keep local state inside |
3541 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3621 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3542 | they do not clal any callbacks. |
3622 | they do not call any callbacks. |
3543 | |
3623 | |
3544 | =head2 COMPILER WARNINGS |
3624 | =head2 COMPILER WARNINGS |
3545 | |
3625 | |
3546 | Depending on your compiler and compiler settings, you might get no or a |
3626 | Depending on your compiler and compiler settings, you might get no or a |
3547 | lot of warnings when compiling libev code. Some people are apparently |
3627 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3581 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3661 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3582 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3662 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3583 | ==2274== still reachable: 256 bytes in 1 blocks. |
3663 | ==2274== still reachable: 256 bytes in 1 blocks. |
3584 | |
3664 | |
3585 | Then there is no memory leak, just as memory accounted to global variables |
3665 | Then there is no memory leak, just as memory accounted to global variables |
3586 | is not a memleak - the memory is still being refernced, and didn't leak. |
3666 | is not a memleak - the memory is still being referenced, and didn't leak. |
3587 | |
3667 | |
3588 | Similarly, under some circumstances, valgrind might report kernel bugs |
3668 | Similarly, under some circumstances, valgrind might report kernel bugs |
3589 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3669 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3590 | although an acceptable workaround has been found here), or it might be |
3670 | although an acceptable workaround has been found here), or it might be |
3591 | confused. |
3671 | confused. |
… | |
… | |
3829 | =back |
3909 | =back |
3830 | |
3910 | |
3831 | |
3911 | |
3832 | =head1 AUTHOR |
3912 | =head1 AUTHOR |
3833 | |
3913 | |
3834 | Marc Lehmann <libev@schmorp.de>. |
3914 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3835 | |
3915 | |